The discovery of Terra Preta soils and the identification of charcoal as an essential component therein initiated an ever-growing research field. Since then, many experiments on the production and application of carbonized plant material (biochar or hydrochar) to soil have been carried out. However, the integration of biochar/hydrochar into soil management systems requires comprehensive analyses to identify and evaluate possible risks and opportunities involved with biochar/hydrochar application. This thesis provides results on the influence of Miscanthus × giganteus feedstock, hydrochar and biochar application on the greenhouse gas balance, plant growth and nutrient status of an extensively managed grassland ecosystem in comparison with an unamended control. The results provide information on the recalcitrance of the carbon amendments against degradation under field conditions. The comprehensive field study was complemented by a greenhouse based plant growth experiment and additional incubation experiments. One of the incubation experiments focused especially on the degradation of the carbon amendments under simulated weather conditions fostering their break down and mineralization. The data gathered in the period of 2011-2014 show an increasingly recalcitrant behavior of the carbon amendments against degradation along their degree of carbonization. As a consequence, both N2O and CO2 losses from the hydrochar and biochar amended soil in the field and in incubation were significantly reduced as compared to the soils amended with uncarbonized feedstock material. Biochar even reduced the CO2 emissions below the control treatment, leading to a significant soil organic carbon increase. The reduction in emissions could not be attributed to a decreasing abundance or activity of soil microorganisms; rather, the results suggested an interaction between biochar and soil- or plant-derived carbon compounds. Over a period of two years, none of the carbon amendments impaired plant growth or reduced the plant nutrient concentrations and nutrient removal. Biochar increased plant growth in a pot experiment in the greenhouse, while hydrochar induced short-term yield decreases in the field. The results suggest that especially and only biochar is suited for long term soil carbon sequestration without negatively affecting the soils greenhouse gas balance or plant growth and plant nutrient concentrations.
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